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July 2, 1963
D. w. DAVIS
3,096,032
LIGHTING DIFFUSER
Filed Sept. 23, 1959
Jim/yaINVENTOR:
. 0.52am
I
34
United States Patent Office
3,096,032
Patented July 2, 1963
2
1
the line 4—-'4 thereof showing the angular pyramids and
depressions.
3,096,032
LIGHTING DIFFUSER
It was heretofore considered necessary to cast or mold
Donald W. Davis, Detroit, Micln, assignor to Lighting
Products, Inc., Highland Park, ill., a corporation of
plastic sheet constructions of this kind particularly those
having accurate projections and depressions rtherein; such
Illinois
molds ‘are provided for limited sections, pieces or areas,
Filed Sept. 23, 1959, Ser. No. 841,776
2 Claims. (Cl. 24€}—10é)
the molds are relatively very expensive and the produc
tion rate is comparatively slow. By extruding a ribbon
or mrip of plastic material of the order of two feet in
This invention relates in general to a sheet plastic dif
fuser with a pattern of projections from one face thereof 10 width using polystyrene and methyl methacrylate and like
preferably made of clear plastic by ‘an extrusion process
and particularly designed for use for an electric lamp
powders ‘with suitable dyes in the eX-truder, a continu
ous sheet of material having a desired pattern and in
lighting diffuser although it may have ‘a more general use
cluding both pyramidal projections and depressions from
wherever applicable.
a given base in one surface ‘of the sheet may be produced
Diffusers of this kind, particularly with a pattern of 15 at a rapid rate.
projections in accordance with this invention, have not
material
in the method
of this of
kind,
producing
it is found
a continuous
desirablesheet
to slightly
of
previously been made by an extrusion process, and the
curve the ribbon or sheet transversely of its length and
present invention made of plastic material is particularly
lconcavely from the pattern side thereof, and after the
desirable as it is expensive to produce molds for making
similar di?users with angular light diffusing surfaces, and 20 extruded portion has been supported and run out a suit
it is difficult to obtain the correct diffusion angle in the
able distance so that it has become su?iciently set or
material on the projections as herein set forth.
An important object of the invention is to produce a
hardened, it is cut off in desired lengths for convenient
handling and use.
Referring now more particularly to the drawings, a
lighting diffuser of clear plastic {with an angular diifusing
pattern in one face with ‘angular depressions extending 25 continuous strip ‘or sheet of a perforated light di?user
construction in accordance with this invention is dis
at the bases of the projections in the material, by ex
charged from a suitable extruder 14 having an outlet or
truded powdered plastic materials in a continuous thin
hopper 16 for receiving the material of which the sheet
sheet.
is made and having suitable mechanism including an exit
A further object of the invention is to provide a plastic
diffuser made in a continuous sheet with projections on 30 die 18 through which the sheet is extruded.
In discharging the sheet which is of suitable width such
one face thereof in a diffusing angular pattern and curv
as 24 inches with a thickness of approximately 135 thou
ing the material transversely of its direction of extrusion
sandths of an inch, it is necessary to support it continu
ously for a time until the material su?iciently sets or
A further object of the invention is to produce a light
ing diffuser of plastic material, plain on one side with 35 hardens, and for this reason, a conveyor represented by
rollers 26 in FIG. 1 extends in front of the extruder
an angular pattern on the other side consisting of pyra
vfor a su?ioient distance. In order to suitably support
mids connected by angular diffusing planes forming de
and reinforce the sheet 12 as it is extruded and for sub
pressions below the normal sides of the pyramids forming
sequent use, it is arched or curved slightly at right angles
the projections.
A still further object of the invention is to provide a 40 to its longitudinal movement transversely of the sheet in
with a slight concave curve in the pattern side.
an are 22 concave at the under side of the extruded sheet
with a radius of the order of two times or more of the
lighting diffuser of plastic material having regular eight
side pyramidal projections extending from one side of the
diffuser with alternate sides of the pyramid connected to
width of the sheet, the pattern side of which is :at the
bottom in FIG. 1, the upper or exposed side 24 being
corresponding sides of adjacent pyramids and extending
angularly below the bases de?ned by the intermediate 45 clear and plain. To cause this curvature, a series of
blowers having nozzles 26 are arranged transversely of
alternate sides of the pyramid.
the path of the sheet at the under side thereof, and in the
Other objects of the invention will appear [in the speci
conveyor as represented by their position between the
?cation and will be apparent from the accompanying
rollers 20 so that the sheet is extruded and carried by the
conveyors, the nozzles discharge air or gas upwardly
drawing in which,
FIG. 1 is ‘a perspective View representing somewhat
diagrammatically the method of extruding a continuous
strip or sheet of a plastic diifuser of this kind having a
regular pattern of pyramidal projections on one side
which is slightly curved transversely ‘and cut off at desired
lengths.
against the under surface of the sheet, cooling it and curv
ing it to form the slight are 2-2 of transverse curvature
and rollers 28 of the conveyor may be slightly larger
or ‘bulging in the center to maintain this curvature.
55
able point, the strip is severed transversely by a cutter
‘343 operated either manually or automatically to out ed
a piece 32v of desired length, a regular length for conven
pyramidal pattern having projections and corresponding
depressions between the depressions with continuous bev
eled sides forming regular pyramidal tops and angular
depressions bet-ween them.
FIG. 3 is a sectional View of a fragment as taken on
the line -3—3 thereof; and
FIG. 4 is a sectional view ‘of a fragment as taken on
When the plastic sheet has been projected sufficiently
from the extruder and carried by the conveyor to a suit
FIG. 2 is a fragmentary plan or face view of a regular
60
ient handling being approximately 48" long.
The diffuser pattern here shown comprises depressions
34 in the form of ‘four sided inverted pyramids extending
‘substantially 23 \thousandths of an inch below the com
mon bases of these inverted pyramids and the sides are
3,096,032
3
4
formed of continuations of the alternate facets 38 of oc
of an inch (entire thickness i135 thousandths minus 55
tagonal pyramidal projections 36 which extend substan
thousandths).
This design of the surface results in eight prismatic
facets ‘for directional concentration of light transmitted
through the panel from the plane side and is more effec
tive than pyramids having fewer prismatic surfaces. By
concentrating the light into a beam having a divergence
tially 55 thousandths of an inch above the common bases
of the pyramids 34 and 36. The total thickness of a
diffuser plate is 135 thousandths of an inch, the width
of the sides at the base of the inverted pyramid is 82
thousandths of an inch, the distance apart of diagonal
apices is approximately 282 .thousandths of an inch and
the angle between such diagonal apices and also the angle
of the sides of the inverted pyramids 34 is 122°.
The dimensions of the projecting and inverted pyramids
is thus given in detail since they are critical to the suc
cessful performance of the plastic extruded sheet as a
of 45° vfrom the base of the beam, measured from the
limits of the transmitting panel, the surface brightness
10 can be kept desirably low. Thus the transmitting panel
lighting diffuser. The depths of the inverted pyramids
concentrates the light into a smaller area and thereby in—
creasing the intensity of the illuminated area. and reduc
ing the glare which results from light escaping at angles
between 45° and the plane of the panel. ‘Fewer prismatic
34 below the common bases of these pyramids and the 15 surfaces will not concentrate transmitted light as elfecé
tively.
'
.
projecting pyramids 36 is thus 23 thousandths of an inch
Instead of being bright and entirely clear, transparent
whereas the projection of the pyramids 36 above said
material, the plastic may also be slightly tinted or colored
common base is substantially 55 thousandths of an inch.
by introducing suitable coloring matter in the plastic
The angles of the sides of the outward and inverted pyra
mids being progressive in the same direction from the 20 mixture as it is extruded. By forming the plastic with a
slight arc therein transversely of its length, the sides of
apices of the inverted pyramids are in the same direction
the plates being usually supported, the weight of the sheet
so that dies of the extruder can be removed freely from
will tend to ?atten this are as the sheet is used which will
the plastic material without damaging it in forming the
support the diffuser in substantially ?at condition in actual
depressions and projections of the diifuser plate.
Thus an accurate pattern of octagonal pyramidal pro 25 use.
The plate may also be pigmented with a suitable mate
jections and square pyramidal depressions are made in
rial in the extrusion process to produce a milk-white in
one face of material producing a multiple of d-i?usiug
stead of a water clear panel for application where re
angular facets completely occupying the space at the dif
?ected glare ‘would be objectionable. The concentrating
fusing side of the sheet, arranged in regular order, the
character of the panel can thus be altered to produce a
octagonal pyramids having alternate sides which extend
wider ‘dispersion by the addition of pigment.
directly into and forming the corresponding sides of the
While this lighting diffuser has been particularly de
inverted square pyramids, which is not true of hexagonal
scribed as desirable for use in connection with electric
and other patterns which of themselves ?t tightly together.
?xtures, it may have a more general use as a light di?user
Plastic panels of this construction are highly desirable
for use in electric lighting ?xtures particularly that type 35 wherever used, the projections and depressions form a
pleasing pattern and design.
in which lamps are located at one side of a plastic naus
While an improved panel like diffuser and the method
parent pattern, usually enclosed in a rectangular or other
of making it by extrusion has been described in some
casing and producing a diffused but bright illumination
detail, the invention ‘should be regarded by way of an
at
construction
the other or
hasouter
the advantage
side of thethat
casing
the,orplastic
?xture.
material 40 illustration and example rather than a restriction or limi
tation thereof, as many changes in the construction, com;
is'light, strong and with multiple facets produces a bright
bination and arrangement of the parts may be made
and shining diifusion which contributes greatly to the
without departing from the spirit and scope of the inven—
desirability of lighting ?xtures which use single or a mul
tiple lighting tube.
tion.
'
In forming the panels used ‘for a lighting diffuser, it 45 This application is a continuation-impart of application
Serial No. 719,642 ?led March 6, 1958, now Patent No.
will be noted particularly from FIG. 2 that the lines of
intersections of the bases of the pyramids are diagonal ' 3,049,616.
I claim:
to the direction of extrusion, substantially at an angle
of 45° by which greater sti?ness is obtained in the rela- '
1. A solid imperforate light diffuser plate of plastic
tively thin panel since the linear crystalline structure of 50 material smooth on one side andhaving octagonal py
ramidal projections and square pyramidal inwardly ex
the plastic, resulting from the extrusion process, is not
tending recesses arranged closely together in the other
parallel to the fracture line between the pyramids result
side of the plate in a regular pattern with the octagonal
ing in greater strength for a panel'of given thickness.
vapices outwardly, the alternate sides of each pyramid
All lines of intersection between adjacent pyramids have
a small radius of approximately 10 thousandths of an 55 meeting the alternate bases of adjacent sides and bases
of adjacent pyramids on all four sides, and the other
inch as shown in FIGS, 2 and 3 which additionally
tour alternate sides of each pyramid extending inwardly
strengthen the panel since two intersecting surfaces tend
in the planes of the sides of the recess, each to meet at
to fracture, when stressed, along the line of intersection
the apex of the recess in the plate forming each of said
between them unless a curved line is provided to dis
tribute the strain over a greater area.
The present panel has regular octagonal pyramids uni
formly. staggered relative to the longitudinal or transverse
access of the extruded strip forming a common line re
pyramidal square inwardly extending recesses, the four’
outward sides of the base of each recess de?ning a com- 7
mon plane ‘for the bases of all of the outward pyramidal
projections, the four common sides of each recess and of
sulting in triangular surfaces extending from the bases 65 the corresponding octagonal pyramids being thus continu
ous and each pair of opposite sides being at an angle of
to the apices of the adjacent pyramids. The opposing
approximately i122".
‘
surfaces of diagonally opposite adjacent pyramids being
2.
A
solid
imperforate
plastic
light diffuser plate
diamond shaped converge in a point. Thus the entire
adapted to be extruded, smooth on one side with octago- '
con?gurated side of the panel is covered with prisms;
nal pyramidal projections, and continuing recesses extend
there are no surfaces which do not contribute to the 70 ing oppositely from a common basis in a regular pattern
directional control of light transmitted from the plane side
on the other side of the plate, the recesses being square
of the panel. ‘By staggering the pyramids, the elfeotive
and the sides of the recesses continuing inwardly to sepa_
thickness of the panel for stilfening purposes is greater
rate apices vfrom the alternate faces of the outward py
than the thickness to the base of the pyramid, that is, it
ramidal projections at the same inclination so the plate
is 80 thousandths of an inch rather than 55 thousandths 75 may be removed at one side of an extruder die, each
3,096,032
.
5
recess lhaving edges in the common base ‘about 82 thou-
6
References Cited in the ?le of this patent
sandths of an inch square, the apex of each square de~
pression being ‘about 23 thousandt‘hs of an inch from said
7
side edges and common base, the height of ‘each octagoI121 pyramid apex above the common base being about 55
‘1,924,294
UNITED STATES PATENTS
Johnson ------------- -- Aug' 8’ 1936
5
1’/ 61,654
Cole ----------------- " Jung 3’ 1930
thousandths of an inch, the plate being 80 thousandths
of ‘an inch thick from the ‘common ‘base of the octagonal
pyramids to the smooth side of ‘the plate and ‘the plate
being about 135 tthousandths of ‘an inch ‘thick from the
smooth side of the plate to the apices of (the octagonal 10
2’491’986
2,546,629
2,640,149
2’8‘19’493
2,859,334
skfll‘ghter ------------- -- OM19’
Emma“ ------------- -- Mar- 27’
Arenkferg ------------ " May 26’
Hawtm et a1 ----------- "" Jan’ 14’
Guth ---------------- -- NOLV' 4’
pyramidal projections‘
2,904,673
Gllih ________________ __ S6111.- 15, 1959
3,001,062
Winkler _____________ __ Sept. 19, 1961
1948
1951
1953
1958
1958